JPH07156395A - Ink jet device - Google Patents

Abstract

(57) [Summary] [Objective] To provide an ink ejecting apparatus having a high yield and excellent mass productivity. [Structure] The ink ejecting apparatus 1 is composed of a piezoelectric ceramic plate 2, an ink supply member 7, a cover plate 10, and a nozzle plate 14. On the piezoelectric ceramic plate 2, a groove 3b having a constant depth and a groove 3a opening to the lower surface of the piezoelectric ceramic plate 2 are formed as the depth gradually increases. An ink inlet 22 and a manifold 21 are formed in the ink supply member 7.
Then, the ink supply member 7 is adhered to the lower surface of the piezoelectric ceramic plate 2, the cover plate 10 is adhered to the upper surface thereof, the groove 3a communicates with the manifold 21 to form an ink chamber, and the groove 3b communicates with the manifold 21. Instead, an air chamber is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet device.

[0002]

2. Description of the Related Art Among the non-impact type printers, which have been expanding the market to replace the impact type printers used up to now, the principle is the simplest, and multi-gradation and colorization are possible. Inkjet type printers are mentioned as being easy to use. Above all, a drop that ejects only the ink drops used for printing
The on-demand type is rapidly spreading due to its good injection efficiency and low running cost.

The Kaiser type disclosed in Japanese Patent Publication No. 53-12138 as a drop-on-demand type,
Alternatively, a thermal jet type disclosed in Japanese Patent Publication No. 61-59914 is a typical method.
Of these, the former is difficult to miniaturize, and the latter requires a high heat resistance of the ink in order to apply high heat to the ink, and each has a very difficult problem.

A method proposed to solve the above defects at the same time is disclosed in Japanese Patent Laid-Open No. 63-247051.
It is the shear mode type disclosed in the publication.

As shown in FIG. 9, the shear mode type ink jet device 600 comprises a bottom wall 601, a top wall 602 and a shear mode actuator wall 603 therebetween. The actuator wall 603 is bonded to the bottom wall 601 and is polarized in the direction of arrow 611.
And an upper wall 605 bonded to the ceiling wall 602 and polarized in the direction of arrow 609. The actuator walls 603 are paired to form an ink flow path 613 therebetween, and a space 615 narrower than the ink flow path 613 is formed between the next pair of actuator walls 603.

The nozzle 6 is provided at one end of each ink flow path 613.
A nozzle plate 617 having 18 is fixed, and electrodes 619 and 621 are provided as metal layers on both side surfaces of each actuator wall 603. The electrodes 619 and 621 are covered with an insulating layer (not shown) for insulating the ink. Then, the electrodes 619, 6 facing the space 615
Reference numeral 21 is connected to a ground 623, and electrodes 619 and 621 provided in the ink flow path 613 are connected to a silicon chip 625 which provides an actuator drive circuit.

Next, a method for manufacturing the ink jet device 600 will be described. First, the piezoelectric ceramic layer polarized in the arrow 611 is bonded to the bottom wall 601, and the piezoelectric ceramic layer polarized in the arrow 609 is bonded to the ceiling wall 602. The thickness of each piezoelectric ceramic layer is as follows.
Equal to 5 height. Next, parallel grooves are formed in the piezoelectric ceramics layer by rotating a diamond cutting disk or the like to form a lower wall 607 and an upper wall 605. Then, the electrode 61 is formed on the side surface of the lower wall 607 by vacuum deposition.
9 is formed, and the insulating layer is provided on the electrode 619.
Similarly, the electrode 621 and the insulating layer are provided on the side surface of the upper wall 605.

The zenith of the upper wall 605 and the zenith of the lower wall 607 are adhered to each other to form an ink flow path 613 and a space 615. Next, a nozzle plate 617 in which the nozzles 618 are bored is adhered to one end of the actuator wall 603 so that the nozzles 618 correspond to the ink flow paths 613, and the other ends of the ink flow paths 613 and the spaces 615 are made of silicon. -Connect to chip 625 and ground 623.

Then, the electrode 61 of each ink flow path 613
When the silicon chip 625 applies a voltage to 9, 621, each actuator wall 603 undergoes piezoelectric thickness slip deformation in a direction of increasing the volume of the ink flow path 613, and after a predetermined time, the voltage application is stopped and the ink flow is stopped. Road 613
Of the ink flow path 61 from the increased state to the natural state.
Pressure is applied to the ink in the nozzle 3, and ink drops are generated in the nozzle 61.
It is injected from 8.

[0010]

However, Japanese Patent Laid-Open No. 63-2 shows an ink ejecting apparatus 600 having the above-mentioned structure.
In Japanese Patent No. 47051, only the ink flow path 613 is filled with ink and the space 615 is not filled with ink, but the specific configuration and method thereof are not disclosed. Therefore, for example, in the bottom wall 601 or the top wall 602, the ink channel 61
3 are provided corresponding to the respective ink flow paths 613 so that ink is supplied only to the ink flow paths 613 and the space 6
If ink is not supplied to 15, it is difficult to form the through holes due to their small size, and the yield is poor. In addition, there is a problem in that it takes time to process and mass productivity is poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an ink ejecting apparatus which has a high yield and is excellent in mass productivity.

[0012]

In order to achieve this object, according to claim 1 of the present invention, an ejection channel through which ink is ejected and a non-ejection channel that is provided on both sides of the ejection channel and in which ink is not ejected. An ink jetting device having a partition wall formed by piezoelectric ceramics, at least a portion of which is separated from the jetting channel and the non-jetting channel, wherein the jetting device is formed on a plate of which at least a portion is made of piezoelectric ceramics. A first groove serving as a channel, and a second groove serving as the non-injection channel formed in the plate without being opened in at least one surface of the plurality of surfaces of the plate where the first groove is opened; The first groove is opened and the second groove is joined to the surface not opened to form a manifold for supplying ink. And a manifold member.

According to a second aspect of the present invention, the first groove is opened on the upper surface, the lower surface and both end surfaces of the plate, and the bottom surface is linearly inclined, and the second groove is formed on the upper surface and both end surfaces of the plate. It is characterized in that it is opened and its bottom surface is formed linearly.

According to a third aspect of the present invention, the first groove is opened on the upper surface and both end surfaces of the plate, and the bottom surface thereof is linearly formed, and the second groove is opened on the upper surface and one end surface of the plate. And its bottom surface is linearly inclined.

[0015]

In the ink jet device of the present invention having the above structure, the manifold member has the first groove opened,
In addition, the second groove is joined to the surface not opened, and the manifold formed in the manifold member is connected to the ejection channel and is not connected to the non-ejection channel, and ink is supplied only to the ejection channel. Ink is ejected from the ejection channel by the deformation of the partition wall.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the ink ejecting apparatus 1 is
It is composed of a piezoelectric ceramic plate 2, an ink supply member 7 as a manifold member, a cover plate 10 and a nozzle plate 14.

The piezoelectric ceramic plate 2 is made of a lead zirconate titanate (PZT) ceramic material, and the piezoelectric ceramic plate 2 is cut with a diamond blade or the like to form a plurality of grooves 3. . The piezoelectric ceramic plate 2 is provided in the groove 3.
3a as the first groove opened on the upper surface, lower surface and both end surfaces of the
And a groove 3b as a second groove opened on the upper surface and both end surfaces of the piezoelectric ceramic plate 2, and the groove 3a and the groove 3b are formed alternately. The bottom surface of the groove 3a is different from the surface (top surface) of the piezoelectric ceramic plate 2 on the groove 3 forming side.
It is linearly inclined so that the depth becomes deeper as it approaches the one end face 15, and is opened in the vicinity of the one end face 15 on the face (lower face) opposite to the groove 3 forming side. Further, as shown in FIG. 3B, the bottom surface of the groove 3b is linearly formed parallel to the surface of the piezoelectric ceramic plate 2 on the groove 3 forming side. The grooves 3 on both outer sides
Is the groove 3b. Further, as shown in FIG. 1, the partition wall 6 which is the side surface of the groove 3 is polarized in the direction of arrow 5.

A metal electrode 8 is formed in the upper region of the inner surface of the groove 3 by sputtering or the like. Also,
As shown in FIG. 2, which shows a plan view of the one end surface 15 of the piezoelectric ceramic plate 2, the metal electrode 8 extends from the side surface of the groove 3 into the one end surface 15 of the piezoelectric ceramic plate 2.

Next, as shown in FIG. 1, alumina, PZ
The cover plate 10 formed of a ceramic material such as T is adhered to the surface of the piezoelectric ceramic plate 2 on the groove 3 processing side with an epoxy adhesive 20 (FIG. 5).

An ink inlet 22 and a manifold 21 are formed in the ink supply member 7 formed by injection molding of a resin material or the like. Further, the ink supply member 7 is provided with a pattern 18 for obtaining electrical contact with the metal electrode 8 formed on the one end surface 15 described above. Then, the ink supply member 7 is bonded to the one end surface 15 of the piezoelectric ceramic plate 2 and the surface (lower surface) opposite to the bonding side of the cover plate 10 with an epoxy adhesive or the like. As a result, the groove 3a and the manifold 21 communicate with each other. Further, the metal electrode 8 and the pattern 18 are electrically connected to each other without providing an adhesive layer serving as an insulating layer in the electrical connection portion between the metal electrode 8 and the pattern 18.

Next, a nozzle plate 14 having nozzles 12 provided at positions corresponding to the positions of the grooves 3a is adhered to the end faces of the piezoelectric ceramic plate 2 and the cover plate 10 opposite to the end faces 15 thereof. This nozzle plate 1
4 is formed of a plastic such as polyalkylene (for example, ethylene) terephthalate, polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.

3 (a) and 3 (b) show cross sections of the ink ejecting apparatus 1 along the grooves 3a and 3b, respectively. As aforementioned,
By adhering the piezoelectric ceramic plate 2, the ink supply member 7, the cover plate 10, and the nozzle plate 14, the ink chamber 4 as an ejection channel corresponding to the groove 3a and the air chamber 27 as a non-ejection channel corresponding to the groove 3b are formed. It is formed. As shown in FIG. 3A, all the ink chambers 4 communicate with the manifold 21 to be supplied with ink and filled with ink, and as shown in FIG. 3B,
The air chamber 27 is not connected to the manifold 21, is not supplied with ink, and is filled with air.

The pattern 24 of the flexible printed board 23 is connected to the pattern 18 (FIG. 1) formed on the ink supply member 7.

Next, the configuration of the control unit will be described with reference to FIG. 4, which is a block diagram of the control unit. The conductive layer patterns 24 provided on the flexible printed circuit board 23 are individually connected to the LSI chip 51, and the clock line 52,
Data line 53, voltage line 54 and earth line 5
5 is also connected to the LSI chip 51. The LSI chip 51 determines which nozzle 12 should eject an ink drop from the data appearing on the data line 53, based on the continuous clock pulse supplied from the clock line 52, and drives the ink chamber 4. The voltage V of the voltage line 54 is applied to the pattern 24 of the conductive layer which is electrically connected to the metal electrode 8 inside. Further, the pattern 24 of the conductive layer and the air chamber 27 that are electrically connected to the metal electrode 8 other than the driven ink chamber 4.
The pattern 24 connected to the metal electrode 8 of
Connect to 5.

Next, the operation of the ink ejecting apparatus 1 of this embodiment will be described. In order to eject ink droplets from the ink chamber 4a of FIG. 5B, a voltage pulse is applied to the ink chamber 4a (here, applying a voltage to a certain ink chamber 4 means A voltage is applied to the facing metal electrode 8 and the metal electrode 8 facing the ink chamber 4 and the metal electrode 8 in the air chamber 27 which are not instructed are grounded). In this case, a voltage is applied to the metal electrodes 8b and 8c so that the air chamber 27
When the metal electrodes 8a and 8d formed on a and 27b are grounded, an electric field in the direction of arrow 13a is generated in the partition wall 6a,
An electric field in the direction of arrow 13b is generated in the partition walls 6b, and the partition walls 6a and 6b are generated by the piezoelectric thickness sliding effect of the piezoelectric ceramics.
And move away from each other. Then, the volume of the ink chamber 4a increases and the pressure in the ink chamber 4a including the vicinity of the nozzle 12 decreases. This state is maintained for the time indicated by L / a. Then, during that time, ink is supplied from an ink supply source (not shown) through the ink introduction port 22 and the manifold 21. The above L / a is the time required for the pressure wave in the ink chamber 4 to propagate one way in the longitudinal direction of the ink chamber 4 (from the manifold 21 to the nozzle plate 14 or vice versa). It is determined by the length L of the ink chamber 4 and the speed of sound a in the ink.

According to the theory of pressure wave propagation, the pressure in the ink chamber 4a reverses and changes to a positive pressure just after a time of L / a from the above-mentioned start-up, but it changes to the ink chamber 4a at this timing. The applied voltage is returned to 0V. Then, the partitions 6a and 6b are in a state before deformation (see FIG.
Returning to (a)), pressure is applied to the ink. At that time,
The positive pressure and the pressure generated when the partition walls 6a and 6b return to the pre-deformation state are added to each other, and a relatively high pressure is applied to the ink in the ink chamber 4a, so that an ink droplet is formed in the nozzle 12. Erupted from.

In the above embodiment, the drive voltage is first applied in the direction in which the volume of the ink chamber 4a increases, then the application of the drive voltage is stopped and the volume of the ink chamber 4a is reduced to the natural state. The ink droplets were ejected from the chamber 4a. First, the drive voltage was applied so that the volume of the ink chamber 4a was reduced to eject the ink droplets from the ink chamber 4a, and then the application of the drive voltage was stopped to eject the ink. Ink may be supplied into the ink chamber 4a by increasing the volume of the chamber 4a from the reduced state to the natural state.

Further, in the above embodiment, a voltage is applied to the metal electrodes 8b and 8c facing the ink chamber 4a for ejecting ink, and the metal electrode 8 facing the ink chamber 4 and the metal electrode of the air chamber 27 which are not instructed. Although 8 is grounded and ink is ejected from the nozzle 12 corresponding to the ink chamber 4a, the metal electrodes 8b, 8 facing the ink chamber 4a ejecting ink.
c is grounded, and the air chambers 27a, 27 on both sides of the ink chamber 4a are provided.
By applying a voltage to the metal electrodes 8a and 8d of FIG.
6b may be deformed to eject ink from the nozzle 12 corresponding to the ink chamber 4a.

As described above, in the ink ejecting apparatus 1 of this embodiment, the groove 3a is opened in the lower surface of the piezoelectric ceramic plate 2 in which the groove 3b is not opened, and the manifold member 17 having the manifold 21 is joined to the lower surface. Therefore, the ink is supplied from the manifold 21 only to the ink chamber 4 formed by the groove 3a, and the ink is not supplied to the air chamber 27. Therefore, the deformation of the partitions 6b and 6c for ejecting ink droplets from the ink chamber 4a does not affect the other ink chambers 4. Therefore, ink droplets are satisfactorily ejected from each ink chamber 4, and the print quality is good. Further, since the air chamber 27 is filled with air, the partition wall 6 is easily deformed and the voltage may be low.

Further, since the groove 3 and the manifold 21 can be easily processed, the yield is high and the mass productivity is excellent.

Further, since the groove 3 is formed so as to penetrate linearly, the cutting speed by the diamond blade can be made constant and the processing time is short.

Next, a second embodiment of the present invention will be described. However, the same parts and equivalent parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, the ink ejecting apparatus 101
Is a piezoelectric ceramic plate 102, an ink supply member 107 as a manifold member, and a cover plate 10.
And the nozzle plate 14.

The piezoelectric ceramic plate 102 is
The piezoelectric ceramic plate 102 is formed of a lead zirconate titanate (PZT) ceramic material, and the piezoelectric ceramic plate 102 is cut with a diamond blade or the like to form a plurality of grooves 1.
03 is formed. In the groove 103, a groove 103a as a first groove having a constant depth and penetrating the one end surface 15 of the piezoelectric ceramic plate 102 and opening, and a groove 103a which becomes linearly shallow as it approaches the one end surface 15 and opens in the one end surface 15. There is a groove 103b as a second groove which is not formed.
a and the groove 103b are formed alternately. The grooves 103 on both outer sides are grooves 103b. Also, the groove 103
The partition wall 106 that is the side surface of is polarized in the direction of arrow 5.

The metal electrode 8 is formed in the upper half region of the side surface of the groove 103a by sputtering or the like. In addition, the metal electrode 8 on the inner surface of the groove 103b is
Since the depth of b is gradually reduced as it approaches the one end face 15, it is finally formed on the bottom surface of the groove 103b. Further, as shown in FIG. 7 which is a plan view of the one end surface 15 of the piezoelectric ceramic plate 102, the metal electrode 8 is provided with the groove 10.
3 is formed so as to wrap around from the inner surface to the one end surface 15.

Next, as shown in FIG. 6, alumina, PZ
The cover plate 10 formed of a ceramic material such as T forms the groove 103 of the piezoelectric ceramic plate 102.
It is adhered to the surface on the processing side with an epoxy adhesive.

Then, the ink supply member 10 as a manifold member formed by injection molding of a resin material or the like.
An ink inlet 122 and a manifold 121 are formed at 7. Further, the ink supply member 107 is provided with a pattern 118 for making electrical contact with the metal electrode 8 formed on the one end surface 15 described above. Then, as shown in FIG. 6, the one end surface 15 of the cover plate 10 and the piezoelectric ceramic plate 102 and the surface of the ink supply member 107 on which the manifold 121 is formed are bonded with an epoxy adhesive or the like. Thereby, each groove 10
3a communicates with the manifold 121. Further, the metal electrode 8 and the pattern 118 are not provided with an adhesive layer serving as an insulating layer in the electrical connection portion between the metal electrode 8 and the pattern 118.
And are electrically connected.

Next, on the end faces of the piezoelectric ceramic plate 102 and the cover plate 10 opposite to the one end face 15,
The nozzle plate 14 provided with the nozzle 12 at a position corresponding to the position of each groove 103a is bonded.

Grooves 103a and 103 are shown in FIGS. 8 (a) and 8 (b).
The section of the ink ejecting device 101 in FIG. As described above, the piezoelectric ceramic plate 102, the ink supply member 107, the cover plate 10, and the nozzle plate 14 are adhered to each other to form the ink chamber 104 as the ejection channel corresponding to the groove 103a and the non-ejection channel corresponding to the groove 103b. The air chamber 127 is formed. As shown in FIG. 8A, all the ink chambers 104
Communicates with the manifold 121, and the manifold 12
The ink is supplied from 1 and filled with the ink, as shown in FIG.
As shown in (b), the air chamber 127 has the manifold 12
No ink is supplied from the manifold 121 and air is filled.

The pattern 24 of the flexible printed board 23 is connected to the pattern 118 (FIG. 6) formed on the ink supply member 107.

Ink jetting device 10 of the second embodiment described above.
The configuration and operation of the control unit No. 1 are the same as those in the first embodiment, and thus the description thereof will be omitted.

As described above, in the ink ejecting apparatus 101 of this embodiment, the groove 103a is opened in the one end face 15 of the piezoelectric ceramic plate 2 in which the groove 103b is not opened, and the manifold 121 is provided in the one end face 15. Since the member 107 is joined, the groove 103a
The ink is supplied from the manifold 121 only to the ink chamber 104 formed by the ink, and the ink is not supplied to the air chamber 127. Therefore, the deformation of the partition wall 106 for ejecting ink droplets from the ink chamber 104 does not affect the other ink chambers 104. Therefore, ink droplets are satisfactorily ejected from each ink chamber 104, and the print quality is good. Also,
Since the air chamber 127 is filled with air, the partition wall 1
06 is easily deformed, and the voltage may be low.

Further, since the groove 103 and the manifold 121 can be easily processed, the yield is high and the mass productivity is excellent.

Further, the groove 103 is provided so that the cutting speed by the diamond blade can be performed most efficiently.
Since it is formed so as to penetrate linearly, the processing time is short.

In the second embodiment, the groove 103 is formed on one surface of the piezoelectric ceramic plate 102. However, the thickness of the piezoelectric ceramic plate is increased to form grooves on both surfaces to form the ink chamber and the air chamber. May be provided.

In the first and second embodiments of the present invention, the width of the air chambers 27, 127 is made smaller than the width of the ink chambers 4, 104, so that the width of the piezoelectric ceramic plates 2, 102 is made smaller. can do.

In the first and second embodiments of the present invention, the piezoelectric ceramic plates 2 and 102 are formed of a lead zirconate titanate (PZT) ceramic material, and the partition walls 6 and 106 are piezoelectrically slipped. It was deformed,
The piezoelectric ceramic plate may be made of a lead titanate (PT) ceramic material, electrodes may be formed on the entire side surfaces of the partition wall, and the partition wall may be piezoelectrically deformed vertically to eject ink.

Further, in the first and second embodiments of the present invention, the cover plate 10 is used and the ink chambers 4, 10 are used.
4 and the air chambers 27 and 127 are formed, two piezoelectric ceramic plates 2 and 102 are used, and the zenith portions of the partition walls 6 and 106 of the piezoelectric ceramic plates 2 and 102 are bonded to form an ink chamber and an air chamber. A chamber may be formed.

[0050]

As is apparent from the above description, according to the ink ejecting apparatus of the present invention, the first groove for supplying the ink to the ejection channel and not supplying the ink to the non-ejection channel. Since the second groove and the manifold can be easily processed, the yield is high and the mass productivity is excellent. Further, the manifold member is joined to a surface in which the first groove is opened and the second groove is not opened, the manifold formed in the manifold member is communicated with the injection channel, and the non-injection is performed. Since the channels are not communicated with each other, the deformation of the side wall for ejecting the ink droplet from the ejection channel does not affect other ejection channels. Therefore, ink droplets are satisfactorily ejected from each ejection channel, and the printing quality is good.

[Brief description of drawings]

FIG. 1 is a perspective view showing an ink ejecting apparatus of a first embodiment of the invention.

FIG. 2 is an explanatory diagram showing one end surface of a piezoelectric ceramic plate of the ink ejecting apparatus of the first embodiment.

FIG. 3 is a cross-sectional view showing the ink ejecting apparatus of the first embodiment.

FIG. 4 is a block diagram showing a control unit of the ink ejecting apparatus of the first embodiment.

FIG. 5 is an explanatory diagram showing an operation of the ink ejecting apparatus of the first embodiment.

FIG. 6 is a perspective view showing an ink ejecting apparatus of a second embodiment of the invention.

FIG. 7 is an explanatory diagram showing one end surface of a piezoelectric ceramic plate of the ink ejecting apparatus of the second embodiment.

FIG. 8 is a sectional view showing an ink ejecting apparatus of the second embodiment.

FIG. 9 is an explanatory diagram showing a conventional ink ejecting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink ejection device 2 Piezoelectric ceramic plate 3 Groove 4 Ink chamber 5 Polarization direction 6 Partition 7 Ink supply member 8 Metal electrode 10 Cover plate 21 Manifold 22 Ink inlet 101 Ink ejection device 102 Piezoelectric ceramic plate 103 Groove 104 Ink chamber 106 Partition 107 Ink supply member 121 Manifold 122 Ink inlet

Claims (3)

[Claims] 1. An ejection channel through which ink is ejected,
An ink ejecting apparatus comprising: a non-ejection channel that is provided on both sides of the ejection channel and does not eject ink; and a partition wall that separates the ejection channel and the non-ejection channel and at least a part of which is formed of piezoelectric ceramics. A first groove formed on a plate of which at least a part is made of piezoelectric ceramics and serving as the ejection channel; and a plurality of surfaces of the plate, in which the first groove is opened, at least one surface of which is not opened. A second groove formed in a plate, which serves as the non-ejection channel, and the first groove is opened, and the second groove is joined to a surface not opened to form a manifold for supplying ink. An ink ejecting apparatus comprising: a member. 2. The first groove is opened on the upper surface, the lower surface and both end surfaces of the plate, and the bottom surface is linearly inclined, and the second groove is opened on the upper surface and both end surfaces of the plate, The ink ejecting apparatus according to claim 1, wherein the bottom surface is formed linearly. 3. The first groove is opened on the upper surface and both end surfaces of the plate, and the bottom surface thereof is linearly formed, and the second groove is opened on the upper surface and one end surface of the plate, and The ink ejecting apparatus according to claim 1, wherein the bottom surface is linearly inclined.